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SubjectRe: SMACK netfilter smacklabel socket match
Casey Schaufler wrote:
> Tilman Baumann wrote:
>> Casey Schaufler wrote:
>>> Smack will eventually bite you if you're not careful, but users of
>>> MAC systems wouldn't be surprised by that.
>> Speaking of the devil...
>> This is exactly what happened to me right now. I have problems with
>> _some_ https connects. The problem lies somewhere in openssl.
>> I did not yet find any clue with strace.
>> Is there some straight forward way to audit/debug LSM interventions?
> strace is probably your best bet, as it will tell you what syscalls
> fail. Your current situation is most likely a case where your program
> running with a label "Foo" is trying to communicate with a service on
> a machine that doesn't talk CIPSO and hence Smack is treating all
> packets to and from that host with the ambient (%cat /smack/ambient)
> label, which is "_" unless you've changed it.

Yea, I just found that out.
I did not expect smack to add netlabels by default. I thought I would
need to configure something before it will start adding netlabels 'on
the wire'.
In my case 'security' is something that should only concern the local
Unfortunately I never bothered to test this before. :-/

If I set /smack/nltype to 'unlabeled' I have effectively shut off the
I guess I'm missing some essential point here.
Sorry to bother you with such trivialities.

btw. I find it very hard to find informations on the various files in
/smack/ and it's respective intention and formating rules.
security/smack/smackfs.c helps a bit.

This is my current setup:
/smack/ambient (default)
/smack/load = _ foo rwx
Unlabeled process work fine.
Labeled processes produce CIPSO labeled packets (which never get any
answer anywhere from the internet)

If i set /smack/nltype to 'unlabled' i don't even get SYN packets out.
(operation not permitted)

Tilman Baumann
Software Developer
Collax GmbH . Boetzinger Strasse 60 . 79111 Freiburg . Germany

p: +49 (0) 89-990157-0
f: +49 (0) 89-990157-11

Geschaeftsfuehrer: William K. Hite / Boris Nalbach
AG Muenchen HRB 158898, Ust.-IdNr: DE 814464942

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